In order to form an organic layer (referred to also as an organic compound layer, for example, a hole injection layer, a hole transport layer, a light emission layer, a hole blocking layer, an electron transport layer, a hole transport layer, etc.) of an organic electronic element, various methods such as a vapor deposition method, a sputtering method, a CVD, a PVD, a coating method utilizing a solvent have been hitherto employed; however, among these, it is known that a wet film formation method such as a coating method is advantageous in view of such as simplification of a manufacturing process, reduction of a manufacturing cost, improvement of a processing property and an application to a flexible element having a large area such as a backlight or an illumination light source. For example, a method to form an organic compound layer on a glass film of the sheet form by a spin coat method is described in Japanese Patent O.P.I. Publication No. 2002-170676. A method to successively form organic compound layers on a glass plate of the sheet form by an ink jet method is described in Japanese Patent O.P.I. Publication No. 2003-142260. Since a film of the sheet form is utilized as a film in any of these methods, an apparatus for manufacturing a full color display element with a large area is large, resulting in high cost. Therefore, study has been made are made on a roll-to-roll method as an economical manufacturing method of an organic electroluminescence element (hereinafter also referred to as organic EL element), which is considered to be useful for a solid emission type full color display element with a large area or writing light source array, as described in Patent Document 1.
As a manufacturing method of an organic EL display comprising a plastic film as a transparent base plate and provided thereon, a cathode, one or two or more light emission layers composed of an organic compound and an anode, a method is known in which the organic light emission layer or layers are formed according to a coating method employing a coating material in which a low molecular weight emission dye is dispersed or dissolved in a polymeric material such as polystyrene, polymethyl methacrylate and polyvinyl carbazole or a coating material employing a polymeric material such as polyphenylenevinylene or polyalkylfluorene together with an appropriate solvent (refer to, for example, Patent Document 1).
At present, as an organic EL material, there are mentioned a low molecular weight material and a high molecular weight material. The low molecular weight material can be purified by sublimation and is likely to purify. Therefore, it can be employed as a highly purified organic EL material and excels in efficiency or lifetime. On the other hand, the high molecular weight material is difficult to purify, and has disadvantages in that performance such as efficiency or lifetime is deteriorated. Therefore, in recent years, study has been made on a wet film formation method employing the low molecular weight material.
It is known that when a sealed element is subjected to heating treatment, heating treatment is carried out at a temperature of less than Tg of the substrate, since heating treatment at a high temperature of not less than Tg of the substrate produces emission unevenness or deformation in the wave form of the substrate, (Refer to Patent Document 2). However, even heating treatment at a temperature of less than Tg of the substrate produces deterioration of lifetime or reduction of emission area. As a result of study, it has proved that a gas barrier property of seal is deteriorated which is considered to result from separation or breakage of a sealing material due to inner stress of the substrate and the sealing substrate on heating treatment at a low temperature.